1. Field of the Invention
The present invention relates to a silicon-on-insulator (SOI) structure formed using a bonding technique, and particularly relates to a manufacturing method of a semiconductor substrate in which a single-crystal semiconductor layer is bonded to a supporting substrate which has an insulating surface, such as a glass substrate or the like. Further, the present invention relates to display devices and semiconductor devices formed using a semiconductor substrate having such an SOI structure, and a manufacturing method thereof.
2. Description of the Related Art
Semiconductor substrates called silicon-on-insulator (SOI substrate), in each of which a thin single-crystal semiconductor layer is formed on an insulating layer, have been developed instead of silicon wafers manufactured by thinly slicing single-crystal semiconductor ingots. In an integrated circuit using a semiconductor substrate, parasitic capacitance of a transistor can be reduced. Thus, the integrated circuit using a semiconductor substrate is effective for speeding up operation and reducing electric power consumption. Therefore, an SOI substrate is applied to high-performance semiconductor devices such as a microprocessor.
As a method for manufacturing SOI substrates, a separation method using hydrogen ion implantation is known (e.g., see Reference 1: U.S. Pat. No. 6,372,609). The separation method using hydrogen ion implantation is a method in which hydrogen ions are implanted into a silicon wafer to form a microbubble layer at a predetermined depth from a surface, a silicon layer (SOI layer) is separated using the microbubble layer as a separation plane, and the SOI layer is bonded to another silicon wafer. In this method, in addition to heat treatment for separating the SOI layer, it is necessary to perform heat treatment in an oxidation atmosphere to form an oxide film on the SOI layer, remove the oxide film, and perform heat treatment at 1000° C. to 1300° C. in a reducing atmosphere, in order to increase bonding strength.
On the other hand, a semiconductor device in which a single-crystal silicon layer is provided over an insulating substrate such as a high heat-resistance glass is disclosed (Reference 2: Japanese Patent Published Application No. H11-163363). The semiconductor device has a structure where the entire surface of a crystallized glass having a strain point of 750° C. or higher is protected with an insulating silicon film, and a single-crystal silicon layer obtained by a separation method using hydrogen ion implantation is bonded firmly to the insulating silicon film.